Electric heater.



Patented Iuly 29, |902.

WITNESSES'. fa v. 95

UNITED STATES PATENT OEEIcE.

WILLIAM S. IIADAWAY, JR., OF NEV YORK, N. Y.

ELECTRIC HEATER.

SPECIFICATION forming part of Letters Patent No. 705,668, dated July 29, 1902. Application filed September 24,1898. Serial No. 691,769. (No model.)

To @ZZ whom it may concern:

Be it known that I, WILLIAM S. HADAWA Y, Jr., a citizen of the United States, residing in the city, county, and State of New York, have invented a certain new and useful Improvement in Electric Heaters, of which the following is a specification.

My present invention relates to an improved means whereby the resistances used for transforming electric into thermal energy in electric heaters are brought into operative structural relation to the diffusion-surfaces.

In order to obtain the quickest and most economical transfer of heat from a given electrothermal resistance, two factors are important: First, it is desirable to secure a minimum thickness of insulator consistent with eective electric insulation, which insulator must of course suffer no deterioration on being heated; second, the transfer of heat should take place through a substance of maximum diffusivity and through a most intimate contact between the resistance and the diffusion-surface.

Mica affords one of the best heat-resistant high insulators known and occurs in thin sheets, which admirably fulfil the Iirst of the conditions above named. It has therefore been proposed to place heating resistancewires against the diffusion-surface, separating the two by a layer of mica; but in orderV at once to secure the intimate contact desirable and to prevent all displacement of the resistance-wires the latter, together with their insulation, must be pressed very iirmly against the diffusion-surface. In practice this has been found to produce a cutting of the mica by the wires and consequent shortcircuiting by contact with the metallic diffusion-surface. This cutting is due to the unequal pressures over various portions of the mica surface exerted by the wires. I have discovered a means whereby this unequal pressure and consequent cutting` of insulation by the resistance-wires may be entirely obviated and at the same time a diffusionwall of copper may be provided in direct and intimate contact with the mica. As is well known, copper is the material of greatest known diffusivity among those practicable for structural purposes.

My invention provides a safe and permanent union within a minimum space and at a small cost of the electrothermal resistance and its associated diffusion-surface.

My invention also covers an improved means whereby resistance-wires may be conveniently shipped, handled, and put in place in the manufacture of all kinds of electric heaters, and particularly in those of the class herein described.

My invention is illustrated in the accompanying drawings, wherein* Figure l is a vertical section of one form of associated resistance and diffusion-surface as disposed during the process of Inanufacture and before being finally united. Fig. 2 is a partial section, on a larger scale, of the same device, showing the relation of the various parts when the structure is completed. Fig. 3 is a vertical section of the same during process of construction, showing the relation ofthe compression-pluri ger to the brass iiXing-ring; and Fi. Ll: is a plan view of a resistance disk carrying the resistance wire applied thereto in accordance with my improvement.

In Fig. l the outer surface to be heated is shown at l in the form of a steel shell, having a plane under surface and surrounded above by an inwardly-narrowing ring 2, forming a basin. My present invention in the form illustrated relates to the means Whereby the necessary electrothermal resistance is brought into structural and operative relation to the steel shell in question. It is to be understood, however, that the form and Inaterial of the outer surface employed in connectie with my improvement is immaterial to the broad spirit of my invention.

In the construction of my improved device I place upon the inner surface of the shell to be heated a layer of copper amalgam of a thickness dependent upon the shape, size, and number of electrothermal resistances to be used as well as upon the pressure 'to be applied thereto. rIhis layer is shown at 3 in Fig. 2. Upon this layer of amalgam place a layer of insulation e, which is preferably of mica, and upon this I place the clectrothermal resistance, shown in the various iigures of drawings as a wire 5. rlhe resistance is then covered by a second layer of mica, and upon this I place a second layer of copper IOO amalgam similar to the first. It is best to imite the outer edges of the mica sheets-as, for instance7 by cementing them with silicate of potash. This prevents entrance of the amalgam between the mica sheets when compressed.

The copper amalgam is made by combining mercury with copper in Various proportions, preferably about eighty per cent. of pure sponge-copper to twenty per cent. of mercury. lVhen fresh, it takes the form of a somewhat stiiic paste, easily applied in layers of any desired thickness.

Upon the composite structure built up as above described I prefer to place a steel compression-plate preparatory to permanently uniting said structure in the following manner: rlhe Iirst step in the final consolidation consists in applying pressure to the compression-plate and squeezing the wires 5 between the mica layers through the medium of the amalgam. One result of this compression is illustrated in 2. As there shown, the mica being pressed upon equally at all points by the pasty amalgam completely surrounds the various resistance-Wires, making close contact with them over almost their entire periphery. At the same time all around the combined wires and mica the amalgam finds its Way, pressing closely into every wrinkle and curve, and finally completely iilling the interior of the basin within the ring` 2, as shown at 3 in Fig. 2. The surroui'iding of the resistance-wires by the mica in the 1nanner shown is one of the important and desirable results of the use of a pasty amalgam as a medium of compression.

Iprefer to construct this device as follows: The first compression is applied by means of a plunger, as 7, which is driven by any wellknown mechanism and serves as a core at the same time for casting the ring 8. The piringer is shown slightly tapered at its end to fa cilitate withdrawal. /Vhile compression is still being maintained through the plunger?" l pour upon the compression-plate 6 and around the end of theplunger a mass of molten brass, which forms a continuous ring 8, held in place under the narrow edge of the ring 2. The heat given out by the molten brass during this process drives off the mercury, and the resulting structure finally comprises the electrothermal resistance, insulation of mica, and metallic copper, the whole roaees pressed strongly into intimate Contact and held firmly in place by the ring S. The result isa heater of maximum dil'iusivity and of great durability.

The wires or other resistance maybe placed and disposed between the layers of insulation in any desired manner; butl have found the device illustrated in Fig. 4: a convenient one for handling and fixing resistance-wires for this purpose, as well as for use in various connections with many kinds of heaters. A sheet of insulating material 9 is out out into the shape desired for the purpose in hand. Mica is preferred for this purpose, although other materials will answer in some cases. rllhe resistance-wire is then sewed into the insulation either by hand or machine and after any pattern desired. In Fig. at the wire is shown as sewed spirally; but any other disposition is within the spiritot my invention. Pieces of insulation thus provided with resistance units can be used single or combined in many forms of heater and possess obvious advantages for shipping, handling, and replacing.

A. great variety of modieations of detail may be made by those skilled in the art without departing from the broad spirit ot inyinvention defined in the following claims.

The method ot' construction involved in the production of this apparatus is claimed by me in a pending application which is a division hereof", and the omission to claim such method herein is not to be taken as dedication thereoi' to the public.

`What i claim isl. ln an electric heater, an outer shellhaving an upturned edge narrowing upward, a resistance within said shell, a layer oi mica under pressure on each side of said resistance, a compression-plate, and a ring between said plate and said narrowed edge.

2. ln an electric heater, an outer shell having an upturned edge narrowing upward, a heat-producing agent and a diffusion agent both within said shell, a compression-plate for closing said shell and a ring of metal cast between the narrowed portion of said upturned edge and said compression-plate- WILLIAM S. IIADAWAY, Jn. Witnesses:

Citas. F. HALs'rnD, HAROLD S. iiiaciiivn.

IOC 

